1. Field of the Invention
The present invention relates to a webbing take-up device having a lock mechanism which prohibits a rotation of a spool in the pull-out direction.
2. Related Art
Among webbing take-up devices, there is known a webbing take-up device in which a so-called ELR (Emergency Locking Retractor) and a so-called ALR (Automatic Locking Retractor) are provided (for example, see Japanese Patent Application Laid-Open (JP-A) No. 10-244905).
In the webbing take-up device disclosed in Japanese Patent Application Laid-Open (JP-A) No. 10-244905, switching is performed between the ALR and the ELR by an ALR mechanism, and the ALR mechanism includes a cam member (a switching cam) that is connected to a take-up shaft (a spool) via a speed reduction mechanism and a disk control (a control disk). When a webbing is pulled out in the pull-out direction from a state where the webbing is fully wound on the take up shaft, an ALR pawl is held by an inhibition portion of the disk control, so the ALR pawl does not engage with the lock mechanism. Accordingly, the webbing take-up device becomes the ELR state.
Meanwhile, when the webbing is fully pulled out from the take up shaft, the ALR pawl is disposed onto an interlocking inhibition portion (a pressing portion) of the cam member. Then, when the webbing rotates in the take-up direction from this state, the ALR pawl rotates to the lock position, so the ALR pawl engages with the lock mechanism. Accordingly, the lock mechanism is operated so that the webbing take-up device is switched to the ALR state.
However, in this webbing take-up device, the cam member is connected to the take up shaft via the speed reduction mechanism as described above. Accordingly, in a case in which the speed reduction ratio of the speed reduction mechanism is set to a large value, the rotation amount of the cam member with respect to the rotation of the take up shaft decreases, so that the switching timing from the ELR (or ALR) state to the ALR (or ELR) state becomes unclear.
Therefore, in a case in which the speed reduction ratio of the speed reduction mechanism is set to a small value, the rotation amount of the cam member with respect to the rotation of the take up shaft increases, so the accuracy for the switching timing from the ELR (or ALR) state to the ALR (or ELR) state may be improved.
However, in this case, since a rotation variation of the cam member increases due to an assembly variation or a variation of components such as the speed reduction mechanism and the cam member, there is a possibility that the ALR pawl climbs over the interlocking inhibition portion of the cam member when the webbing is fully pulled out from the take up shaft. Thus, it is desirable to obtain a structure capable of absorbing a rotation variation of the cam member while improving the accuracy for the switching timing from the ELR (or ALR) state to the ALR (or ELR) state.